Answer:
The correct answer is: upper esophageal sphincter.
Explanation:
The alimentary canal is a very long tract responsible for the digestion of the food. It is composed of several organs with many different and important functions. The alimentary canal also has a few sphincters, which are muscular valves that open and close when needed for the food to pass or be retained.
The first sphincter is the upper esophageal sphincter. One particularity of this sphincter is that is one of the few sphincters in the body that opens and closes under our conscious control, which happens when we decide to swallow our food.
From the first to the last, the order of the sphincters in the gastrointestinal tract is: upper esophageal sphincter, lower esophageal sphincter or gastroesophageal sphincter, pyloric sphincter, ileocecal sphincter, and anus.
Answer: The environment changed suddenly from a shallow ocean setting to a river system.
Explanation: Changes seen in rock layers represent changes in Earth's local history. The rock layer stack overall shows a shallow ocean setting. But the youngest layer at the top was deposited by a river. This shows the geologist that the local environment changed suddenly from an ocean setting to a river system.
The right answer is chromosome > DNA > gene.
Living cell element, of characteristic shape and in constant number, located in the nucleus of the cell.
DNA, which is our chromosome, carries the genes
. The DNA molecule, also known as deoxyribonucleic acid, is found in all our cells.
The gene is a piece of this DNA that corresponds to a particular genetic information that codes for a single protein. So it's a very small portion of chromosome.
It has meanwhile been shown that the most sensitive cells are those that areundifferentiated, well nourished, dividing quickly and highly active metabolically. Amongst the body cells, the most sensitive are spermatogoniaand erythroblasts, epidermal stem cells, gastrointestinal stem cells.
Hoped this helped!
